Environmental chamber

ABSTRACT

An environmental chamber wherein conditions of temperature, humidity, and daylight are simulated to most nearly approximate conditions found in nature. The chamber uses an Xenon lamp as a light source to closely simulate natural sunlight. Within the chamber, light from the Xenon lamp is changeably filtered so as to produce light conditions that nearly approximate the varying sun conditions which exist throughout a typical normal day at a particular location. Temperature and humidity are controlled by air conditioning and heating systems that are programmed to produce atmospheric conditions within the chamber in simulation of actual environmental conditions.

United States Patent Mallory 1 July 17, 1973 ENVIRONMENTAL CHAMBER [75]Inventor: Roy E. Mallory, Salt Lake City, Utah [73] Assignee: MalloryEngineering Inc., Salt Lake City, Utah [22] Filed: Apr. 7, 1971 [21]Appl. No.: 131,879

[52] US. Cl. 165/20, 165/22 [51] Int. Cl F24f 3/14 [58] Field of Search165/19, 20, 21, 22,

[56] References Cited UNITED STATES PATENTS Beeler l65/22 PrimaryExaminer-Charles Sukalo Attorney-B. Deon Criddle ABSTRACT Anenvironmental chamber wherein conditions of temperature, humidity, anddaylight are simulated to most nearly approximate conditions found innature. The chamber uses an Xenon lamp as a light source to closelysimulate natural sunlight. Within the chamber, light from the Xenon lampis changeably filtered so as to produce light conditions that nearlyapproximate the varying sun conditions which exist throughout a typicalnormal day at a particular location. Temperature and humidity arecontrolled by air conditioning and heating systems that are programmedto produce atmospheric conditions within the chamber in simulation ofactual environmental conditions.

9 Claims, 10 Drawing Figures Patented July 17, 1973 4 Sheets-Sheet 2 FIG6 INVENTOR. ROY E. MALLORY ATTORNEY Patented July 17, 1973 4Sheets-Sheet 3 NATURAL DAYLIGHT F I G 7 XENON LIGHT ASSEMBLY 900NANOMETERS F I G 8 WAVE LENGTH IN 25 CUT OFF AT 265 MM.

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IN NANOMETERS WAVE LENGTH INVENTOR.

INCANDESCENT ROY E. MALLORY FLOURESCENT a INCANDESCENT XENON LIGHTSOURCE GROW LUX ATTORNE- Patented July 1 7 1973 3,746,080

4 Sheets-Sheet 4 FIG 9 20 zone (3* zone (2} zone (4) X FIG IO ENERGY INMICROWATTS LJL NH.

ZONE

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300 400 800 800 700 B00 900 I000 IIOO I200 I300 I400 I000 WAVE LENGTH INNANOMETERS (*3 NATURAL SUNLIGHT I=0O P.M., EARLY AUGUST, 4,000 FT. MSL-INVENTOR. ROY E. MALLORY EEQM m ATTORNEY ENVIRONMENTAL CHAMBER BRIEFDESCRIPTION OF THE INVENTION 1. Field of the Invention This inventionrelates to chambers wherein atmospheric conditions includingtemperature, humidity, and sunlight are artificially simulated toclosely approximate conditions found in nature such that actual plantgrowth, and other botanical, physiological, chemical, ecological andbiological responses to such conditions can be studied in a laboratory.

2. Prior Art Until now, laboratory structures for artificiallysimulating natural atmospheric conditions have failed to provide anadequate light source with which natural sunlight could be accuratelyapproximated. U.S. Pats. Nos. 3,l08,399 and 3,124,903, for example, showsuch chambers using incandescent and flourescent lighting systems. Sofar as I am aware, however, the prior art devices have not succeeded'insimulating all of the varying degrees of intensity of sunlight thatexist during the passage of a normal day.

While the prior art structures have somewhat successfully reproducedconditions of temperature and humidity and, by using flourescent andincandescent type light sources have reproduced parts of the sunspectrum, they have not achieved a spectral distribution pattern orlight intensity level that is truly representative of natural sunlight.Flourescent and incandescent light sources, do not duplicate that partof the natural light spectrum which plants utilize in theirphotosynthesis processes, for example, nor do they provide the lightintensities necessary to studies of atmospheric conditions onpollutants.

Neither, to my knowledge, has anyone heretofore attempted to filter orchange the intensity of a light source such that varying conditions oflight intensity that occur during a typical day from sun up to sun downare simulated. The present invention provides an accurate simulation ofnatural atmospheric conditions of light, light intensity, temperature,and humidity so that a controlled environment exists wherein plantgrowth and development experiments and other condition responsiveexperiments can be investigated under the various conditions developed.

SUMMARY OF THE INVENTION It is a principal object of the presentinvention to provide an environmental chamber wherein conditions mostnearly approximating those found in nature can be accurately simulatedand maintained.

Another object is to provide an environmental chamber having a lightsource which closely approximates most of the plant growth portion ofthe spectrum of natural sunlight.

Still another object is to provide a variable light filter system whichenables the Xenon light within the chamber to be filtered toapproximately the varying light conditions which exist in nature duringthe passage of an actual day.

Principal features of the invention include a cabinet made up ofseparate and distinct compartments one of which serves as a growth ortesting chamber wherein environmental conditions are reproduced and theother of which houses the support apparatus necessary to produce desiredconditions within the growth chamber. The growth chamber can be sealedwhile in use and observations can be made through a glass window in anaccess door. The window has a door which can be positioned to seal itwhen observations are not being made and it is desired to preventvariations due to loss of light or entrance of light through the window.

Polished stainless steel walls provide reflective surfaces within thegrowth chamber, and a light reflector above a light source cooperateswith the walls to disperse light rays from a central light sourcethroughout the chamber.

A liquid cooled Xenon arc lamp is used as the light source for thechamber and is positioned in the center of the cabinet and near the roofso that generated light energy is directed onto samples or specimenpositioned below it. The Xenon light source operates at high wattagelevels, generally from five thousand to six thousand five hundred watts,depending upon the age of the lamp, to provide a high energy light thatradiates a spectrum closely conforming to the spectrum of naturalsunlight and particularly to that portion of the spectrum necessary tophotosynthesis of plants.

Another feature is a light filter system that includes a sheet of filmplastic, or'similar material, which is colored or smoked to varyingdegrees of opaqueness. The sheet is mounted to be drawn across thechamber between the Xenon light and samples in the chamber so that thelevel of light intensity is varied beneath the filter. Filter movementcan be controlled manually or automatically by a programmer whichregulates filter movement to cause the light emitted from the Xenonlight source which-is sensed below the filter, to approximate inintensity the varying levels of sunlight a plant, in its natural state,would sense during the passage of a day being simulated or to simulatethose light intensities to which smog pollutants, such as automobileemissions, are subjected during the day being simulated.

The growth or testing chamber of the invention also includes an aircirculating blower to direct air flow through the interior of thechamber; a humidifier assembly, to introduce moisture into the chamber;a dehumidifier coil, to remove moisture from the air in the chamber;heating and cooling assemblies, to produce desired temperatures; andducting for directing air movement and for introducing new air into thesystem.

The apparatus for supporting the equipment in the growth chamber ishoused in an equipment enclosure chamber which has a recording and.control means for directing and programming the system apparatussuitably arranged on a front panel.

Additional objects and features of the invention will become apparentfrom the following detailed description and drawings, disclosing what ispresently contemplated as being the best mode of the invention.

THE DRAWINGS In the drawings:

FIG. 1 is a front elevation view of the environmental chamber of theinvention;

FIG. 2 a top plan view;

FIG. 3 a section taken on the line 33 of FIG. 1, showing the interior ofthe chamber as viewed from the top;

FIG. 4a section taken on the line 4-4 of FIG. 2, showing the interior ofthe chamber as viewed from the front;

FIG. 5 an exploded, perspective view of the Xenon light, its coolingjacket assembly, and a sheet-type light filter assembly; 7

FIG. 6 a schematic diagram showing the operational components of thegrowth chamber;

FIG. 7 a chart comparing the spectral energy distribution of a Xenonlamp with that of natural sunlight;

FIG. 8 a chart comparing the spectral energy distribution of an Xenonlamp with that of other types of light sources;

FIG. 9 a chart showing the various zones of light intensity within thechamber; and

FIG. 10 a chart showing the energy level of each zone of lightintensity, as shown in FIG. 9.

DETAILED DESCRIPTION Referring now to the drawings:

The environmental chamber 20 shown in FIGS. 1-4, consists of a cabinethaving a front wall 21, side walls 22a and 22b, and a back wall 23. Aninner panel 24, ex-

tending between walls 21 and 23 separates a growth chamber 25, from anequipment enclosure chamber 26. A door 27, hinged at 270 and 27b andhaving a locking handle 270, allows access to the interior of growthchamber 25. An observation window 28 is lo- 'cated in door 27 and awindow access door 29, hinged at 290 and 29b to door 27 provides a lightseal for the window. Cooperable locking latch components 290 and 29d onthe doors 29 and 27, respectively, provide means for locking door 29over the window. When door 29 is opened observation of. conditionswithin the growth or testing chamber 25 can be made without extensivelydisrupting the atmospheric conditions therein.

The walls, top and bottom and sides of the growth chamber are all doublewalls with a layer 30 of insulation between them. This insulationshields the interior of the growth chamber from conditions existingexterior to the chamber. A tray 31, FIG. 4, holds test samples and canbe selectively positioned on tray supports 31a that project inwardlyfrom the front and back walls at any desired height within the chamber.A diurnal filter 32, shown installed in the growth chamber in FIGS. 3and 4, and exploded therefrom in FIG. 5, consists of a filter screen 33,which is colored or smoked to have different degrees of opaqueness alongits length. The filter screen 33 is pulled from a spring tensioned reel34 by a motor 35 that turns a reel 36. Cables 33a and 33b are fixed toan end of screen 33 and are connected to reel 36. As reel 36 is turnedby motor 35 to wind the cables, and thereafter the screen 33 thereon,the screen is pulled off reel 34. Reversal of motor35 will allow theconventional spring mechanism of the reel 34 to rewind the screen. Themotor 35 is geared such that tension is maintained in the screen whenthe motor is not operating. The movement of filter screen 33, beneath alight source 37, changes the light intensity within the chamber beneaththe screen in accordance with the opaqueness of the portion of thescreen stretched beneath the light source.

It should be understood that a plurality of overlying filter screens andoperating means therefor may be used, depending upon the amount ofintensity surpression that is desired, and that other filter means maybe employed. For example, a sleeve-type filter, not shown, havingvarying degrees of opaqueness in its wall, could be driven to rotatearound the chamber light source.

The light source 37, shown best in FIG. 5, consists of a water cooledXenon tube 38. The Xenon tube very closely reproduces the portion of thesun spectrum used by plants during photosynthesis. The Xenon Bulb 38 isaxially mounted between end housings 39 and 40, and inside a pyrex-glasstube 41 and a surrounding outer water jacket 42. Coolant liquid iscirculated between tube 41 and the outer water jacket 42. Hex nuts 39aand 40a are respectively threaded onto housings 39 and 40 and couplecoolant hoses 42a and 42b and an electrical conduit 43 to the lightsource. Water or other suitable coolant is pumped into the assemblythrough hose 42a and after it is circulated between the tube 41 and thejacket 42 it flows out through the hose 42b. The Xenon tube 38 normallygenerates intense heat during its operation which heat is transmittedthrough the pyrex .glass tube 41, to be absorbed in and carried off bythe water flowing between tube 41 and water jacket 42. The pyrex glasstube 41 and/or the coolant may be tinted to provide some filtering ofthose light waves generated from the Xenon tube 38 which are notinvolved in plant photosynthesis. The cooling of the Xenon tube alsogreatly prolongs the life of the tube, thereby making it economicallypractical for use in the chamber.

A light reflector 44, positioned within the growth chamber 25, above thelight source assembly 37, together with the stainless construction ofthe chamber, directs light from the Xenon tube 38 downwardly to wardsthe bottom of the chamber 25. As can be seen from FIG. 9, which shows achamber with light zones marked thereon and FIG. 10 which shows therelative energy distribution from the Xenon tube 38 within the zones ofFIG. 9, the energy levels are maintained substantially constantthroughout the entire growth chamber.

The close approximation of the light produced by natural daylight andthat produced by the light source 37 is shown by the chart of FIG. 7. Asdetermined by use of a spectro radiometer, the energy level inmicrowatts per square centimeter, per nanometer is determined andplotted for various light ray frequencies throughout the light spectrumof natural sunlight at 2:00 P.M., Mountain Daylight Savings Time at SaltLake City, Utah, elevation 4,200 feet. Similarly, the spectro-radiometeris used within the chamber 20 to determine the energy level of thevarious wave lengths produced by light source 37 and the figuresobtained are plotted. As can be seen in FIG. 7, the curves formed byconnecting the plotted energy levels of natural sunlight and of thegenerated light are very close through the entire spectrum rangeplotted, i.e., 300 nanometers to 1,500 nanometers. This spectrum rangeincludes all light having any significant effect on plant photosynthesisand includes the significant ultra-violet rays in the 280500 nanometerrange; the visable light rays in the S00-l,100 nanometer range, both ofwhich kinds of rays contribute significantly to plant photosynthesis;and the infrared rays in the l,l00-l,500 nanometer range, which produceheat necessary to cause normal plant sweating. While some incidentalenergy spikes are produced by the present lighting system that greatlyexceed the energy level of normal daylight, these are so infrequent andare of such short duration that they are not shown on the graph and haveno practical effect on the lighting system or its use.

The chart clearly demonstrates the lack of similarity of light emittedfrom the Xenon light assembly to the other commercially available lightsources. The chart shown in FIG. 8 represents spectral comparisons oflight emitted from the Xenon light assembly 37 with other light sourceswhich have been used in other environmental chambers as substitutes fornatural sunlight.

An air supply duct 45 circulates air from a fan 46 over the sample tray31 and through a return duct 47. Support equipment, comprising a coolingcoil 48, a dehumidifier coil 49, electric heating elements 50, and ahumidifier assembly 51 are all positioned within the air flow system,between the return air duct 47 and the circulating fan 46. Air passingthrough the growth chamber 25 and out of return duct 47 is reconditionedby these components before it is again circulated by fan 46 back throughthe supply duct 45 into the growth cham ber. The air is circulated bothbelow and above the filter screen 33 when the screen is pulled out bymotor 35 and is stretched substantially between the front, back and sidewalls. Thus, no damaging heat build up occurs above the screen.

The growth chamber 25 is separated from the support equipment by aflooring 52. The extent of conditioning performed on air to becirculated through the growth chamber is regulated electrically from acontrol panel 70 which is located on the front of the equipmentenclosure 26.

The equipment enclosure contains support and command apparatus forprogramming and directing the functions involved in creating desiredenvironmental conditions within the growth chamber 25. This support andcommand apparatus includes a lamp power control housing 53, anelectrical box 54, a refrigeration condensing unit 55, and a lampcooling system consisting of a heat exchanger 56 and pump 57. Atemperature humidity recorder chart 71 is mounted to have its chart faceviewable at the front wall 21 of the equipment enclosure 26. Therecorder thus provides an easily viewed, continuous, chronologicalrecord of the temperature and humidity within the chamber.

In FIG. 6, the component relationships are schematically illustrated andthe overall operation of the chamber is best explained in connectionwith the schematic illustration of the interaction of the equipment andapparatus within the environmental chamber. As illustrated, the lampassembly 37 may consist of an Osram Xenon Arc Lamp housed in an assemblyof the type heretofore described. The lamp assembly is water cooledthrough an inlet line 58 and an outlet line 59, respectively connectedto the outlet 56a and inlet 56b of the heat exchanger 56. The heatexchanger 56 has a coil 560 through which coolant is circulated andtemperature responsive switch 5611 that is in contact with the watercirculated through the heat exchanger to be responsive to thetemperature thereof. A lamp cooling pump 57 pumps water from the heatexchanger 56 into the inlet line 58 and through a de-ionizing filter 57ato the Xenon lamp assembly 37.

A water pressure failure switch 57b is connected electrically to thelamp power circuit so that, should the water pressure fall below apredetermined value, i.e., 5 p.s.i., power to the lamp is automaticallycut off, thereby preventing overheating of the lamp. The watertemperature responsive switch 56d is also connected electrically to thelamp circuit so that should the water temperature exceed a set point(120 F. for example) the lamp will be turned off.

As has been previously explained, the diurnal filter 32 is positioned bya motor 35, which is controlled by a diurnal cycle timer 60.

In normal operation, air is circulated from blower 46, through supplyduct 45 and into the chamber. The air moves through the interior of thechamber, and is returned through the air duct 47 to blower 46. A drybulb temperature sensor 61 and a wet bulb temperature sensor 62 arelocated in duct 47. These sensors generate electrical signals which arefed to a temperature controller 63, which may be a Honeywell model R7306A w/55P140D0l0, for example, and a humidity controller 64, which maybe a Honeywell model R7306B w/SSPl40D020. The controllers act to compareactual conditions of the air within the return air duct 47 withprogrammed condtions sent to them from a programmer 65. As shown, aconventional phyhrometer assembly 66, supplies water to the wet bulbwick of the wet bulb temperature sensor 62.

Depending upon the program established for programmer 65, as determinedby an operator who sets the control dials of control panel 70, theprogrammer 65 and the actual conditions sensed by sensors 61 and 62, thetemperature controller 63 will cause heating or cooling of the airbefore it is forced into the chamber by fan 46. If heating is requiredtemperature controller 63 actuates the electrical heating elements 50while at the same time turning off the air cooling equipment used. Ifair cooling is required, temperature controller 63 deenergizes theheating elements 50 and opens a valve 67. Opening of valve 67 permitswater to flow from the refrigeration condensing unit 55 through a valve68 and into and through the cooling coil 48. From the cooling coil, thewater flows through a suction shut off valve 69, through a suctionregulator 72, and into a suction accumulator 73. Thereafter it flowsback to the refrigeration condensing unit 55. When the water from thecondensing unit has sufficiently cooled the air flow, the water isdiverted through a liquid injection shut off valve 74 through valve 75and back to the suction accumulator 73. Cycling of the refrigerationcondensing unit 55 occurs if the suction pressure is not maintained at adesired level, i.e., approximately 10 psi. Therefore, to avoid cyclingwhen the demand for air conditioning stops, with a resultant drop incompressor suction, a hot gas, by-pass shut off valve 76 is opened todivert discharge gas from the refrigeration condensing unit 55 through ahot gas, by-pass valve 77 and to the suction accumulator 73, therebymaintaining suction pressure at the desired valve.

Conditions of humidity are transmitted to the humidity controller 64,where they are compared with conditions set into the programmer 65 by anoperator setting the-dials of control panel 70. If it is determined bythe controller 64 that additional moisture content is needed thecontroller 64 opens the humidifier inlet valve 78 thereby permittingwater from the stream sup ply to flow to the humidifier assembly 51.Shoud conditons sensed in the return air duct 47, as compared withconditions set into the programmer 65, indicate that the returning airshould be dehumidified, the humidity controller 64 closes humidifierinlet valve 78 and opens dehumidifier inlet valve 79. Coolant water isthereby allowed to flow from the refrigeration condensing unit 55,through a check valve 80 and into the dehumidifier coil 49, where thecold water acts to condense moisture from air passing the coil. Thewater is then returned to the refrigeration condensing unit 55 through adehumidifier regulator valve 81.

Electricity is supplied to the various valves, pumps, motors, heatingelements, controllers, etc. from the electrical box 54, with electricalenergization, operation and control of the Xenon lamp assembly beingsupplied from the lamp power control housing 53 in conventional fashion.Because of the high operating heat generated by the Xenon lamp, the lampcircuit includes the water termperature responsive switch 56d and thewater pressure failure switch 57b to insure that lamp cooling isavailable when the lamp is operating. The lamp power control housing 53contains timers which initiate lamp ignition by firing a lamp ignitor.The timers are deactivated when lamp ignition is sensed.

The control panel '70 also mounted thereon various monitor gauges, whichindicate conditions within the growth chamber; programming means forsetting indesired environmental conditions; and switches for energizing,deenergizing, and controlling electrical circuits to the variousapparatus within the chamber.

While the invention has been particularly described as being useful forplant growth studies, it has many other uses. For example, air pollutionstudies can be made using the environmental chamber and particularlystudies of the effects of sunlight on emitted pollutants and possiblepollutants can be made in the laboratory.

Although a preferred form of my invention has been herein disclosed, itis to be understood that the present disclosure is by way of example andthat variations are possible without departing from the subject mattercoming within the scope of the following claims, which subject matter lregard as my invention.

1 claim:

1. An environmental chamber comprising an enclosure having a top;

a bottom;

end walls interconnecting said top and said bottom;

side walls interconnecting said top, bottom, and

end walls;

a light generating source producing light having a spectrum closelyapproaching that of natural daylight positioned close to and beneath thetop;

circuit means connecting said light generating source to a source ofelectricity filter means below the light generating means and above thebottom; means for positioning said filter means to stretch substatniallybetween the end and side walls;

air conditioning means having means for circulating air through thechamber above and below the filter means, means for heating thecirculated air, means for cooling the circulated air, and means foradding moisture to the air; and

means, including a control panel on the chamber for establishing airtemperature, and humidity in the chamber.

2. An environmental chamber as in claim 1, wherein the filter meanscomprises a rolled screen of partially opaque material.

3. An environmental chamber as in claim 2, wherein the means forpositioning the screen comprises a spring-type reel on which the screenis wound, a take-up reel at least one cable connecting an end of thescreen and the take-up reel and a reversible motor arranged toreversibly drive the take-up reel.

4. An environmental chamber as in claim 3, wherein the filter meanscomprises a plurality of filters of different degrees opaqueness; and

the means for positioning said filter means comprises programming meansto selectively position the filters whereby the lgiht spectrum at theside of the filters opposite the light generating source can be variedas necessary to coorrespond to natural daylight spectrum.

S. An environmental chamber as in claim 4, wherein the plurality offilters are continuously connected to form the roller screen.

6. An environmental chamber as in claim 4, wherein at least some of thefilters are arranged to be stretched in layers beneath the Xenon lamp.

7. An environmental chamber as in claim 1, wherein the light generatingsource is an Xenon lamp.

8. An environmental chamber as in claim 7, further including means forcontinuously circulating a coolant around the Xenon lamp.

9. An environmental chamber as in claim 1, wherein the filter meanscomprises a plurality of filters of different degrees opaqueness; and

the means for positioning said filter means comrpises programming meansto selectively position the filters whereby the light spectrum at theside of the filters opposite the light generating source can be variedas necessary to correspond to natural daylight spectrum.

1. An environmental chamber comprising an enclosure having a top; abottom; end walls interconnecting said top and said bottom; side wallsinterconnecting said top, bottom, and end walls; a light generatingsource producing light having a spectrum closely approaching that ofnatural daylight positioned close to and beneath the top; circuit meansconnecting said light generating source to a source of electricityfilter means below the light generating means and above the bottom;means for positioning said filter means to stretch substatnially betweenthe end and side walls; air conditioning means having mEans forcirculating air through the chamber above and below the filter means,means for heating the circulated air, means for cooling the circulatedair, and means for adding moisture to the air; and means, including acontrol panel on the chamber for establishing air temperature, andhumidity in the chamber.
 2. An environmental chamber as in claim 1,wherein the filter means comprises a rolled screen of partially opaquematerial.
 3. An environmental chamber as in claim 2, wherein the meansfor positioning the screen comprises a spring-type reel on which thescreen is wound, a take-up reel at least one cable connecting an end ofthe screen and the take-up reel and a reversible motor arranged toreversibly drive the take-up reel.
 4. An environmental chamber as inclaim 3, wherein the filter means comprises a plurality of filters ofdifferent degrees opaqueness; and the means for positioning said filtermeans comprises programming means to selectively position the filterswhereby the lgiht spectrum at the side of the filters opposite the lightgenerating source can be varied as necessary to coorrespond to naturaldaylight spectrum.
 5. An environmental chamber as in claim 4, whereinthe plurality of filters are continuously connected to form the rollerscreen.
 6. An environmental chamber as in claim 4, wherein at least someof the filters are arranged to be stretched in layers beneath the Xenonlamp.
 7. An environmental chamber as in claim 1, wherein the lightgenerating source is an Xenon lamp.
 8. An environmental chamber as inclaim 7, further including means for continuously circulating a coolantaround the Xenon lamp.
 9. An environmental chamber as in claim 1,wherein the filter means comprises a plurality of filters of differentdegrees opaqueness; and the means for positioning said filter meanscomrpises programming means to selectively position the filters wherebythe light spectrum at the side of the filters opposite the lightgenerating source can be varied as necessary to correspond to naturaldaylight spectrum.